Tinning depth control



Nov- 26, 195 N. D. KORBITZ TINNING DEPTH CONTROL 2 Sheets-Sheet 1 Filed Sept. 19, 1956 ZNVENTOR NORMAN D. KORBITZ Nov. 26, 1957 N. n. KORBITZ TINNING DEPTH CONTROL.

2 Shets-Sheet 2 Filed Sept. 19, 1956 INVENTOR NORMAN o. KORBITZ BY ATTORNEY TINNING DEPTH CONTROL Norman D. Korbitz, Burlington, Iowa, assignor to Sylvania Electric Products Inc., a corporation of Massachusetts Application September 19, 1956, Serial No. 610,738

8 Claims. (Cl. 118-7) This invention relates to immersion depth control mechanism. The invention is exemplified in conjunction with the tinning of electron tube lead wires, but the principles evolved in this disclosure are applicable to the immersion of any article to a desired depth in any liquid having an electro-conductive medium on its surface.

In many applications, it is desirable to immerse an article in a liquid to a precise depth and then remove the article from the liquid. In the past, depth of immersion has been controlled by the amount of displacement of a movable member carrying the article with respect to the liquid container. But with such criterion the depth of immersion varied with variations in height of the liquid within the container. As disclosed herein, the depth of immersion is controlled by precise locating of an article in a holder, which holder is provided with a contact, and by the level of the liquid in which the article is immersed. By reason of such control the coatings on the article immersed is always brought within a predetermined distance of a fixed level on the article.

It is therefore, an object of this invention to provide a means whereby precise heights of coatings relative to a fixed level on an article may be applied thereto.

In the manufacture of electron tubes with long flexible lead-ins, it is necessary to tin substantially the entire length of wires to facilitate soldering operations and for other purposes and yet it is requisite that the tinning not be deposited on the base of the electron tube, else short circuiting of the tube leads would ensue. Some specifications require that the leads be tinned to within .050" of the tube base making the untinned distance very small and difficult of attainment. It is, specifically, an object of the invention to provide a timing mechanism which shall permit the tinning of wire leads of an electron tube to within an exceedingly small distance of the base of the tube and without immersion of the base of the tube within the tinning material.

The above and other objects will become apparent upon consideration of the following specification when taken in conjunction with the accompanying drawing in which:

Fig. 1 is a perspective view of a portion of a machine for tinning wire leads of an electron tube, parts being broken away to expose otherwise hidden portions, and

Fig. 2 is a wiring diagram explanatory of the operation of the machine.

Referring to the drawings in greater detail, at there i is indicated a fixed post having a base 12 surmounted by a metallic tinning pot 14 containing aconventional tinning composition 16. The pot may be heated in conventional fashion by an electric heater, not shown, connected to the terminals of the pin plug'18. The pot also has a binding post 20 tapped into it to which a conductor 22 is attached.

Fixed in any suitable manner to the upper end of the post. is a double acting cylinder 24 of which the piston has piston rod 26 extending downwardly from the cylin- -der. At its lower end there is afiixed a combined tube and contact carrier 28 which is generally T-shaped with atent O ice a tube clip 30 at one end of the horizontal bar of the T and a contact 32 at the other end of the bar. The carrier is alfixed to the piston by a set screw 34, or the like, engaging a key way 36 on the piston. To prevent the carrier from rotating relative to the post, the post has integrated therewith, as by welding, a plate 38, apertured to permit sliding therein of the piston rod 26 and also of a guide rod 40 fastened at its lower end to the leg of the T-shaped carrier 28. The upper end of the rod 40 may slide through a suitable aperture in cylinder flange plate 42 and in the rear of the cylinder. The clip 30 is a conventional spring clip designed to frictionally retain an electron tube when inserted in the clip.

Also adjustably mounted on the post as by the bracket 42 and bolts 44 and 46 passing through horizontal and vertical slots 48, 50, respectively, in bracket portions is a locator cylinder 52. Slidable within the cylinder is a piston 54 having a piston rod 56. The piston and piston rod are normally urged to the right hand end of the cylinder by a coil spring 58 reacting between the forward head of the cylinder and the forward face of the piston. A fluid pressure inlet 60 is provided at the rear end of the cylinder. The piston rod, by suitable adjustment of the bolts 44 and 46 and inclination of the bracket 42, is

vent piston rod rotation. At the forward end of the piston rod is a seat 61 adapted to move into a vertical plane below the clip 30 so as to permit a tube inserted in the clip to be pushed down against the seat, when the piston 26 is fully raised, thus using the seat as a reference level. When the piston 56 is retracted into the cylinder by action of spring 58, the seat 61 is out of the path of movement of the carrier 28 and parts carried thereby. The contact 32 heretofore referred to is threaded through the carrier and held in an adjusted position therein by the lock nut 62.

To the screw contact there is affixed the lead wire 64 as by the use of lock nuts 66. On the lower end of the contact screw 32 is aflixed a carbon tip 68 which has the property of not having tin adhere to it when dipped in and removed from the tinning bath 16. The lower end of the carbon tip is adjusted to be just level with the height of tinning desired on the lead-in wires 70 of tube 72. Thus if it were desired that the tinning on the wires should extend to .050 of the bottom of the electron tube or envelope, the contact screw 32 would be adjusted so that the lower end of carbon tip 68 is .050" below the level of the bottom of the envelope. Then as the carrier descends, the end of the carbon tip will contact the material of the tinning bath just as the tinning of the lead-in wires proceeds to within .050 of the bulb.

Mechanism is now provided to move the carrier down toward the tinning bath, automatically halt when a desired tinning level of lead-ins is attained, then, after a delay, return the carrier to original position. Also auto matic mechanism is provided to move the locating seat in and out of position in timed relation to the movements of the carrier.

This mechanism will now be described.

Adverting to Fig. 2, it will be noted there is a pair of main electric conductors and 82. The conductor or line 82 may be considered as the line at ground potential. In the conductor or line 30 is a fuse 84 and an operator operated switch 86. A tell tale neon lamp 88 bridges the lines 80 and 82 behind the switch 86, and is provided to indicate when the switch 36 is on. Also in line 80 is provided a single pole double throw switch 90, normally in the position shown and feeding the remainder of line 80. Across the lines 80 and $2 is a motor 92 here shown as rotating in a counterclockwise direction. This motor drives a shaft 94 on which are mounted a small sectored cam 96, a large sectored cam 98 and a medium sectored cam 100. The cam 96 closes a normally open switch 102 in a line leading to a thermal switch 104 within a tube and which switch is closed when the filament 106 in the tube is hot. Also serially connected with the tube is the solenoid 108 of a three way valve 110 having fluid pressure inlet 112, fluid pressure exhaust 114 and a fluid conductor port to a conduit 116 leading to the inlet port 60 of locator cylinder 52. When the switches 102 and 104, are closed, the solenoid 108 is energized to cause the valve 110 to assume the position shown in order that the locator seat may be in tube locating position immediately below the clip. The thermal switch is utilized to prevent operation of the locator seat into operative position should the cam 96 have been left by some previous operation in switch closing position, as when switch 86 is opened at the end of the day, and should the piston rod '26 have sunk to lowered position because of non-application of fluid pressure to its piston. Then, when fluid pressure is turned on and switch 86 is closed, the fluid pressure is effective to raise the piston rod 26 and its carrier 28 before the filament 106 heats up sufficiently to allow switch 104 to close. Thus, in starting up the machine, thrusting of the seat 61 to its operative position is retarded until after the carrier 28 is raised. Breakage of parts is thereby prevented. The double throw switch 90 is provided to enable a mechanic to adjust the position of the locator seat in operated position and without operation of other parts. By throwing the switch onto line 120, the switches 102 and 104 are shorted out and the valve 110 and cylinder 52 are operated without motor operation.

The large sectored cam 98 closes a normally open switch 122 in series with a second solenoid 124 and another normally open switch 126, the said switches and solenoid being across the lines 80, 82. The solenoid 124 controls the operation of a second three way valve 128 which controls the inlet and exhaust of fluid into the top of cylinder 24 as through a conduit 130. With the switches 122 and 126 open, the conduit 130 is open to vent, and during Working periods of the mechanism the piston of the cylinder 24 is frictionally held in the last set position of the piston.

In between the switch 122 and the solenoid 124 the line is tapped and a conductor 132 leads to a third solenoid 134 operative to control the flow of fluid through a third three way valve 136. The circuit through the solenoid 134 is completed when the carbon tip 68 makes contact with the surface of the tinning bath 16. Then the circuit to the solenoid is completed to line 82 via the conductor 22 between the metal tinning pot, or a metal rod immersed in the tin bath, and the line. A fourth solenoid 138 is electrically in parallel with the solenoid 134 and is energized with solenoid 134 when tip 68 contacts the tinning bath. When solenoid 138 is energized, a holding circuit for the same and solenoid 134 is established via its contacts 140 and 142, contact 140 being connected to the lower potential end of solenoid 138 (and also of solenoid 134) and contact 142 being connected to line 82. As a result, even when contact tip 68 moves upward and out of contact with the bath, the contacts 140, 142 will still be closed and the solenoids 134 and 138 still be energized. When the switches 122 and 126 are closed and the solenoid 124 is energized, the valve 128 will be turned to admit fluid pressure above the piston in cylinder 24 to lower the carrier 28. At this time the valve 136 is turned to vent the portion of the cylinder below the piston. When the tip 68 contacts the tin in the bath, the solenoid 134 is energized to turn the valve 136 to apply pressure to the cylinder beneath the piston so that now fluid pressure is applied to both sides of the piston and further downward movement of the carrier is halted. Any creeping movement of the piston due to possible differential pressures on the piston is resisted by frictional contact between piston and cylinder or if desired sufficient differential pressure to compensate for the weight of piston and carrier and piston areas may be applied to the two faces of the piston. The length of time the wires 70 will remain in the bath depends on the length of arc of the medium sectored cam 100. When this cam leaves the switch 126, the switch will open, deenergizing solenoid 124 so that valve 128 turns to venting position for the upper cylinder portion. Since solenoid 134 is still energized through the holding of switch 122 closed by the large sectored cam 98, the inlet of fluid via valve 136 to below the piston is continued and the piston and carrier will rise to their upper limits. When the cam 98 leaves its switch both solenoids 138 and 134 will be de-energized, and valve 136 will turn to the venting position shown in Fig. 2. The tube in the clip will then be unloaded and a new one loaded in its place. The cams 96, 98, 100 turn sufficiently slowly to give the operator time to effect the exchange of tubes. Of course the functioning of the apparatus is also under control of the operator at switch 86, which may be a foot or knee operated switch. The cam sector 96 is positioned relative to the other cams so that it engages switch 102 after cam 98 leaves its switch 122 and so that it leaves the switch 102 before switches 122 and 126 are closed thereby enabling the locator seat to be withdrawn prior to downward movement of the carrier. Cam 100 is orientated on the shaft to close switch 126 immediately after cam 98 closes its switch 122, and to open switch 126 the predetermined time desired after wire 70 immersion in the tinning bath.

While this invention has been exemplified as applied to the coating of lead-in wires of electron tubes, it is obvious that the tinning bath may be replaced by any other conductive liquid or if a non-conductive liquid be used, a floating conductive element connected to line 82 may be used. It is also obvious that the object to be coated need not necessarily be an electron tube.

Having thus described my invention what is claimed as new is:

I. A coating mechanism comprising a tank for containing a coating fluid having a conductive medium associated with its surface and rising and falling with the level of said surface, a carrier movable in a direction toward and away from the surface of the fluid, means for so moving the carrier, a support for an article to be coated carried by the carrier, an electrical contact movable with the carrier, and means on downward movement of the carrier and controlled by engagement of the contact with the conductive medium to arrest the moving means and thereby halt further downward movement of the carrier.

2. A coating mechanism comprising a tank for containing an electroconductive coating fluid, a carrier movable in a direction toward and from the surface of the fluid, means for so moving the carrier, a support for an article to be coated carried by the carrier, an electrical contact movable with the carrier, and means controlled by engagement of said electrical contact with the surface of the fluid to arrest the moving means and thereby halt further downward movement of the carrier.

3. A coating mechanism comprising a tank for containing an electroconductive coating fluid, a carrier movable in a direction toward and from the surface of the fluid, means for so moving the carrier, a support for an article to be coated mounted on said carrier, a shiftable locator at a fixed elevation above said tank adapted to be engaged by said article to determine its position with respect to the carrier, an electrical contact movable with the carrier, and means controlled by contact of said electrical contact with the surface of the fluid to arrest the carrier moving means and therefore halt further movement of the carrier toward said surface.

4. A coating mechanism comprising a tank for containing an electroconductive coating fluid, a carrier movable in a direction toward and from the surface of the fluid, means for so moving the carrier, a support for an article to be coated mounted on said carrier, a shiftable locator at a fixed elevation above said tank adapted to be engaged by said article to determine its position with respect to the carrier, an electrical contact movable with the carrier, and means controlled by contact of said electrical contact with the surface of the fluid to arrest the carrier moving means and therefore halt further movement of the carrier toward said surface, and means for subsequently moving the carrier away from the surface of the fluid and back to starting position.

5. A coating mechanism comprising a tank for containing an electroconductive coating fluid, a carrier movable in a direction toward and from the surface of the fluid, means for so moving the carrier, a support for an article to be coated mounted on said carrier, a locator at a fixed elevation above said tank adapted to be engaged by said article to determine its position with respect to the carrier, means moving in synchronism with the movements of the carrier for moving said locator into position to be engaged by said article and out of said position, an electrical contact movable with the carrier, and means controlled by contact of said electrical contact with the surface of the fluid to arrest the carrier moving means and thereby halt further movement of the carrier toward the surface.

6. A coating machine comprising a tank for containing an electroconductive fluid, a carrier movable from a fixed upper limit position toward the surface of the fluid and back to its upper limit portion, means for supporting an article on said carrier, an article locator at a fixed level above the tank movable into and out of position below a supported article to enable the same to be located with reference to the carrier and the locator, a contact carried by and movable with the carrier, means for moving the carrier, means for moving the locator in synchronism with the movement of the carrier, and means operative as a result of engagement of the contact with the surface of the fluid to halt the movement of the carrier toward the surface.

7. A coating machine comprising a tank, a carrier having an article support movable from an initial position downward toward and then upward away from the tank and a member having a horizontal seat movable horizontally toward and from the support, an electrical contact movable with the carrier, a motor driven shaft, cams on the shaft, and means operated by one of the cams to first cause movement of the seat toward the article support and then retract the same, means operated by the second and third of the cams to move the carrier toward the tank, means operative on engagement of the contact with conductive material in the tank to halt downward movement of the carrier and on continued rotation of the cams to move the carrier upward to its initial position.

8. A coating machine comprising a tank adapted to contain an electroconductive fluid connected to an electrical lead, a vertical cylinder above the tank, a double acting piston in said cylinder with a pair of three-way valves controlling the flow of fluid to and from the cylinder, a piston rod of said cylinder extending below the cylinder and mounting an article support and an electrical contact, a single acting cylinder on a fixed horizontal axis, said single acting cylinder having a piston rod extending radially toward the support, a seat on the end of the piston rod adapted to seat an article positioned in the article support when the single acting piston is forced toward the support, a spring retracting the single acting piston, a driven shaft, three cams on said shaft, a switch in series with a solenoid controlled by the first of said cams, said solenoid being operative to control the flow of fluid to the single acting cylinder, the second and third of said cams each controlling a switch, respectively, said second and third cam controlled switches being in series with each other and with a second solenoid, means controlled by said second solenoid to admit fluid into and vent the double acting cylinder above its piston via the first of said pair of three-way valves, said second and third cams having larger sectors than the first cam and positioned to close their switches after the first cam has opened its switch, the second cam being a larger sector than the third cam, a third solenoid in series with the contact on the carrier and connected between the switch operated by the second cam and the second solenoid, the second of the pair of three-way valves being operated by said third solenoid and connected to supply fluid to and vent the fluid from beneath the piston of the double acting cylinder and a self locking relay bridging the third solenoid with its locking contact connected to said electrical lead.

References Cited in the file of this patent UNITED STATES PATENTS 2,508,200 Tarlton May 16, 1950 

